Mike McDonald is a senior associate with Pollara Strategic Insights and chief strategy officer for Kirk & Co. He served as chief of staff to former B.C. premier Christy Clark.

Ontario voters will render their verdict on Thursday. The Liberals have governed since 2003, but it’s now clear that it’s not a matter of if there’s change but, rather, what kind of change – either Doug Ford’s PCs or Andrea Horwath’s NDP.

The outcome will be a major tone-setter for national politics and influence the makeup of the issues heading into the 2019 federal election, not to mention the impact it would have on one of the largest subnational economies in the world.

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Of course, only those who actually vote get to decide. There are more than 10 million eligible voters, but there have never before been more than five million voters in an Ontario provincial election. Millions of Ontario residents will sit it out, leaving the participants to decide.

It also matters where they vote. Government is decided by the makeup of 124 seats, not a beauty contest of overall votes.

The most recent B.C., Alberta and federal elections provide insight into what could happen in Ontario.

Both Stephen Harper and Christy Clark may have been satisfied if they were told in advance of their recent re-election bids that they would retain the same number of votes as the previous election – and they actually did. However, in both cases, the voter pool expanded while theirs stood still. Basic math tells us that if the number of voters increases, your party’s market share will decrease if it does not grow.

In the 2015 federal election, 6.5 million Ontario residents cast a vote – far higher than a typical Ontario election. Will provincial voter turnout continue to lag significantly behind federal turnout, or will hordes of new voters bust down the doors and alter market share? Advance turnout is up 18 per cent over 2014.

Older voters have disproportionate influence because they are more likely to vote. In low-turnout elections, their influence is even greater. In B.C.’s 2017 election, fewer than 30 per cent of eligible voters under the age of 24 voted, compared with almost 70 per cent of those aged 65 to 74.

During the course of the election campaign, the NDP have made gains across the board, and they are also doing better with older voters. If this remains the case, they will have gone great lengths in neutralizing a key support base for Doug Ford’s PCs. However, if the PCs prevail with older voters, the NDP will need to counteract this disadvantage by increasing turnout among younger voters. They would need to dilute the PC’s market share by motivating non-voters to vote.

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Our firm has tracked the enthusiasm each party’s supporters has for their voting preference. Doug Ford’s supporters are the most fired up relative to the Liberals and the NDP. They are also more likely to say they will “definitely” vote. This is a good sign for the PCs. The danger is if Liberal voters’ enthusiasm to stop Doug Ford leads them to switch to the NDP. Now that Liberal Leader Kathleen Wynne has conceded the election, has she motivated Liberal voters to vote NDP to stop Mr. Ford?

So far, NDP backroom strategists have likely been high-fiving each other based on the first three and a half weeks of the campaign. They’ve seen this before – in Alberta in 2015. The narrative of the campaign has followed a similar course – once again, we have a discredited incumbent government and an official opposition, with new leadership, working in real-time to shape a winning coalition. Enter Andrea Horwath as Rachel Notley, looking to come from third to first.

Like Ms. Notley in 2015, Ms. Horwath will have a disadvantage in converting votes to seats. Had Alberta 2015 been a close race in terms of popular vote, it is unlikely the NDP would have been able to form a government with even a five-point win in the popular vote. Its votes were concentrated in Edmonton. Ms. Notley needed to win big on popular vote and, guess what, she did. She won by 12 points and, with it, a majority.

In Ontario, even if Ms. Horwath was leading the polls, would she be leading in seats? The modelling of who wins what seats based on the popular vote indicates that Doug Ford’s PCs are much more efficient in terms of how their votes are spread across the province. The NDP could blunt the PC age advantage, blunt the PC voters’ enthusiasm and could win the popular vote and still lose the election. To form government, the NDP will need to wallop the PCs.

Who votes, and where they vote, will decide who governs Ontario. It is hardly a groundbreaking theory, but one that is commonly forgotten. Will Ontario voters stay on the couch or will they take a more active role in setting the course for their province and, indeed, the country in the year ahead?

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